Centrifugal compressors in some gas compression systems require diffusers to convert the gas accelerated by the impeller of the centrifugal compressor into pressure energy, and to reorient the gas so that it flows parallel to the longitudinal center axis of the compressor for passage downstream. Mixed-flow compressor stages have a downstream stator that orients the discharge from a mixed-flow rotor so that it is parallel to the center axis. Reorienting the gas flow imposes relatively high flow turning or diffusion, and thus results in aerodynamic losses which affect the overall efficiency of the compressor. Because compressor diffusers, such as diffuser pipes downstream of an impeller for example, take up considerable space it would be desirable to obviate the need for such diffusers entirely. It would also be desirable to increase the pressure ratio of the compressor relative to standard impeller-diffuser pipe configurations.